Waterproofing glossary

Hydrostatic pressure — the pressure water in saturated soil exerts against your foundation. It is why sealers fail: a coating with pressure behind it blisters off. It is what drainage systems are designed to relieve.

Drain tile / weeping tile — perforated pipe laid in washed stone and wrapped in filter fabric, which collects water and carries it to a discharge point or sump. 'Tile' is a historic term; it is plastic pipe today. A footing drain is drain tile at the base of the foundation on the outside. An interior perimeter drain is the same idea inside, under the basement floor slab, priced at $40-$120 per linear foot (Fixr, 2026).

Sump pit and sump pump — the pit is the basin water collects in; the pump lifts it out through a discharge line. A check valve in that line stops discharged water flowing back into the pit. Installation typically runs $800-$2,000 (Fixr, 2026).

Dimple board — dimpled plastic sheeting that creates an air gap between soil and wall so water drains down to the footing drain instead of pressing on the wall. Membrane — a continuous sheet or liquid-applied waterproof skin on the exterior wall. Sodium bentonite — clay that swells on contact with water to self-seal, $2-$5 per square foot (Fixr, 2026).

Efflorescence — white crystalline mineral salt deposits left when water evaporates out of masonry. Evidence of water movement, not mold. Damp-proofing — a thin asphaltic coating that slows moisture vapor, common on older foundations, and not capable of holding back liquid water under pressure. Vapor barrier — sheeting that keeps wall moisture off finished surfaces, $1,500-$4,000 installed (Fixr, 2026). Grading — the slope of the ground away from the house; the code target is at least 6 inches of fall in the first 10 feet (2021 IRC R401.3).

How to choose

If a quote uses a term you don't know, ask

A contractor who can't explain 'dimple board' or 'check valve' in plain words is a problem. A good one will enjoy explaining it.

Watch for damp-proofing sold as waterproofing

They are different products with different capabilities. Ask which one is being installed and get the product data sheet.

Learn 'hydrostatic pressure'

It is the single concept that explains why sealers fail and why drainage works. Understanding it changes how you read every quote.

Proprietary names hide generic products

Branded 'systems' are often standard pipe, fabric, stone, dimple board and a pump. Ask what the generic equivalent is.